1. Field of the Disclosure
The present disclosure relates a system and method for enabling the recovery of services for a user equipment (UE) from a forbidden public land mobile network (PLMN) in a mobile communication system.
2. Description of Related Art
In a typical mobile communication environment, a UE may communicate voice and/or data signals with one or more service networks via cellular stations of the service networks. With the advancement of wireless communications, machine type communication (MTC) has been developed, which enables remote machines to exchange information and operate without human interaction. MTC sensors may be employed to monitor the operations and report measurement results back to service networks via wireless communication networks. The wireless communication between the UE and the service networks may be in compliance with various wireless technologies, such as, for example, global system for mobile communications (GSM) technology, general packet radio service (GPRS) technology, enhanced data rates for global evolution (EDGE) technology, wideband code division multiple access (WCDMA) technology, long term evolution (LTE) technology, LTE-Advanced technology, and others.
In the cellular communication networks, service networks broadcasting their PLMN identities (IDs). The UEs may carry out automatic network selection based on preferences of the PLMN IDs stored in a GSM subscriber identity module (SIM) or a universal subscriber identity module (USIM). In the automatic selection mode, the UE selects a PLMN from a preferred PLMN list in a predetermined priority order. Typically, the UE also includes a forbidden list, which includes PLMN IDs that are not permitted to be used under normal data service conditions. Conventionally, the UE may remove any PLMN ID from the preferred PLMN list, that is also present in the forbidden list, before network selection, so that the UE may not select the forbidden PLMN for normal data services.
FIG. 1 is a diagram illustrating a handover zone between a first PLMN, PLMN A and a second PLMN, PLMN B. A UE 102 previously added PLMN B 106 in a forbidden PLMN list. Thus, while in PLMN A 104 region, the PLMN B 106 is forbidden for UE 102. The UE 102 is mobile and establishes a circuit switching/packet switching (CS/PS) call in the PLMN A 104. The UE 102 enters into handover zone 108 of the PLMN A 104 and the PLMN B 106, where the PLMN A 104 can give a handover command to the UE 102 to go to the PLMN B 106, which has a roaming agreement with the PLMN A 104.
FIG. 2 is a diagram illustrating representing a UE that does not trigger a circuit switched/packet switched (CS/PS) registration procedure upon receiving a forbidden PLMN in a dedicated message.
Referring to FIG. 2, for example, the present disclosure assumes that the UE has a “forbidden PLMN list” 210 or a “forbidden PLMNs for GPRS service” list, wherein the “forbidden PLMN list” 210 or “forbidden PLMNs for GPRS service” list includes PLMN A 212 as the UE's home PLMN on Network 1 206, PLMN B 214 of Network 2 208. In step 213a, the UE transmits a CS/PS call request to the RRC 204 through the NAS 202, and in step 213b, the RRC 204 transmits the CS/PS call request to the Network 1 206. In step 216, the UE establishes a CS/PS call in the PLMN A 212 through non-access stratum (NAS) 202 in mobility of the UE.
In step 218, the UE enters into a handover zone of the PLMN A 212 and the PLMN B 214 through radio resource controller (RRC) 204. The PLMN B 214 is indicated through the RRC 204 dedicated signaling. In step 219a, the network 1 206 transmits a handover to PLMN B 214 command to the RRC 204. In step 219b, the RRC 204 notifies transmit success of the handover to the PLMN B 214. In the step 219c, the RRC 204 transmits a request to update the PLMN B 214 on the network 2 208 as the UE's home PLMN in the “forbidden PLMN list” 210 or “forbidden PLMNs for GPRS service” list. Once the handover is successful, in step 220, since the PLMN B 214 is still a forbidden PLMN, a registration procedure may not be triggered. Since the PLMN B 214 is still a forbidden PLMN, in step 222, the PLMN 214 is a roaming PLMN on a current area. In step 224, the CS/PS call ends, and, in step 226, the RRC 204 camps on the PLMN B 214. In the 227, the RRC 204 transmits PLMN B 208 available indication to the NAS 202. In step 228, even though the PLMN B 214 is available, the UE assumes that the PLMN B 214 is still a forbidden PLMN and registration procedure may not be triggered. The UE may be in limited service in the PLMN B 214 after the service is ended. This may unnecessarily delay the services of PLMN B to the user. In step 230, the PLMN B 214 is still the roaming PLMN in current area.
With the existing approach, the UE cannot access the communication services in the PLMN B since the PLMN B is in a forbidden PLMN list, even though the PLMN B has a roaming agreement with the PLMN A. When the PLMN B is forbidden, the UE starts a “Forbidden PLMN list deletion timer”, and the PLMN B is not available until the timer expires or until the PLMN B is manually selected. The situation may worsen when there is no PLMN available in a particular area other than PLMN B. In such a case, the UE may remain in a state of limited service until the forbidden PLMN lists are erased. This further unnecessarily delays the services of PLMN B to the user.